The present invention relates to a U-shaped iron core transporting/assembling method in a transformer transported in a disassembled condition and a U-shaped iron core transporting/assembling tank used in the method.
In recent years, voltage to be supplied to a transmission system increases with an increase in electric power demand. Accordingly, the capacity, size, and weight of stationary induction electric appliances, such as transformers, used for power transmission/transformation increase.
Transformer stations in which a transformer is installed are often located in sites with severe transport conditions, such as mountain area or underground of urban areas. Therefore, it is necessary to significantly reduce the transportation dimension and weight of the stationary induction electric appliance installed in such sites.
In such a case, a disassembled transportation method capable of significantly reducing the transportation scale and weight of a product to be transported has been adopted as a transportation method of the transformer. In this method, a large capacity three-phase transformer, etc. that has already been produced and tested in a factory is disassembled into several components: a U-shaped iron core, yokes, coils, and the like, then the components are housed in transportation tanks specially designed for the respective components to their installation site, and the respective components are reassembled in, e.g., a clean house built at the installation site. A transformer transported using the above disassembled transportation method is referred to as “disassembled transportation transformer”.
Recently, as disclosed in Japanese Patent Application Laid-Open Publication No. 2007-67112, the entire content of which is incorporated herein by reference, the U-shaped iron core is disassembled further into smaller parts (e.g., leg iron core and lower-yoke iron core) in order to reduce the size of each component to be transported.
The clean house used for assembling the disassembled transportation transformer at its installation site generally has two rooms: an assembling room and a spare room and has a structure in which framed support column are surrounded by a panel unit constituted by a plurality of plate materials. Each room has a roof at the top. The roof is constituted by a framing material and a water-proof sheet and extensively attached to the framing so as to be opened and closed. A dehumidifier, a dust collector, and the like are provided in both the assembling room and spare room for controlling the humidity or dust amount in the rooms. In general, it takes about 20 days to build up the clean house.
The U-shaped iron core that has been divided into the leg iron core, lower-yoke iron core, and the like and transported to the installation site is carried in the spare room where dehumidification and dust removal have been accomplished and unpacked from a transportation tank, etc., and then carried into the assembling room where dehumidification and dust removal have been accomplished, by a tow truck, etc.
However, the on-site iron core assembling method of the disassembled transportation transformer has the following problems.
For example, an iron core of a large capacity three-phase five-leg transformer is constituted by four U-shaped iron cores. Thus, it is necessary to assemble the four U-shaped iron cores at the installation site after the assembling room of the clean house has been built up. In general, it takes about 7 days to complete the assembly of one U-shaped iron core. In the space of a conventional assembling room where the U-shaped iron core is assembled, it is possible to assemble at most two U-shaped iron cores simultaneously, in general. In this case, it takes about 14 to 17 days to complete the assembly of all the U-shaped iron cores. Thus, it takes more time to install the entire transformer than in the case of a general disassembled transportation transformer where the iron core is transported in the form of the U-shaped iron core by the time length required for assembling the U-shaped iron core at the installation site.
Further, the above work schedule is applicable to only a case where the weather is stable. For example, it is necessary to open the roof of the assembling room when the iron core is carried into the assembling room, so that the carry-in work cannot be performed in the case of rain, delaying the installation.
Further, carry-in of the leg iron core and yoke iron core and carry-out of an erection tank in which the U-shaped iron core is housed and erected need to be performed using a tow truck. Hoisting up/down of the iron core by a tow truck needs to be performed at both the assembling room and spare room. The tow truck is parked in the intermediate portion between the assembling room and spare room and, there, the hoisting up/down of the leg iron core and yoke iron core is performed in a state where the arm of the tow truck is extended in an inclined manner. Thus, a tow truck with large hoisting capacity is required. The rental fee, etc., of such a tow truck with large hoisting capacity is high, and there is no other way but to rent a tow truck whose per-unit time rental fee is high in order to assemble the U-shaped iron core, causing increase in cost.
Further, the carry-in of the leg iron core and yoke iron core often needs to be performed many times, and every time the carry-in work is performed, the roofs of the spare room and assembling room need to be opened. When the roofs are opened, a large volume of external air is introduced inside the spare room and assembling room, so that it is necessary to perform dehumidification and dust removal every time the roofs are opened, which may cause delay of the installation.